The present invention relates generally to a method of manufacturing pulp and more particularly to a method of manufacturing pulp to be used for making corrugated medium.
A wide range of methods exist for manufacturing semi-chemical pulp to be used for making a corrugated medium. For example, the high yield hardwood pulps used in manufacturing corrugating medium may be produced using semi-chemical pulping processes including soda/caustic pulping, neutral sulfite semi-chemical (NSSC) pulping, and green liquor pulping. Depending on the manufacturing method used, the pulp yield generally varies from 75 percent (%) to 82% for NSSC pulping and up to 85% to 86% for green liquor and soda/caustic pulping. Typically low yields pulps result from treatment with sulfur containing cooking chemicals, which provide better pulp quality than high yield pulps.
Standard soda/caustic (SC) pulping is a popular method for puling. SC pulp manufacturing is attractive due to inexpensive cooking chemicals and a relatively easy and simple chemical recovery process. The pulp quality from standard soda/caustic pulping tends to be inferior to the pulp quality generated by NSSC pulping. The pulp quality is a major disadvantage for soda/caustic pulping, especially for paper grades requiring high results for the ring crush test and corrugated medium test (CMT).